In some cases, an inverter used in power converters is formed with an insulated gate bipolar transistor (IGBT) and a free wheeling diode (FWD) that are connected in antiparallel. The FWD connected to the IGBT in this manner operates to protect the IGBT by preventing a reverse current from flowing in the IGBT.
In order to downsize the inverter, there has been proposed a semiconductor device with the IGBT and the FWD formed on the same semiconductor substrate a so-called reverse-conducting IGBT (RC-IGBT). But the respective operating characteristics of the IGBT and the FWD when formed on the same semiconductor substrate have to be improved to improve the operating characteristics of the reverse-conducting IGBT.